500 Scientists to Share Findings on Nature of Light

May 25, 1995

"All these 50 years of conscious brooding have
brought me no nearer to the answer to the question,
"What are light quanta?" Nowadays every Tom, Dick and
Harry thinks he knows it, but he is mistaken." --
Albert Einstein in 1951.

After studying light and its most fundamental particles,
photons (or light quanta), for more than half a century, even
Albert Einstein had difficulty understanding and explaining the
subject. So it should come as no surprise that, nearly 45 years
later, hundreds of scientists around the world are still seeking
answers to the most basic questions about the nature of light and
photons.

More than 500 of these scientists from five continents will
descend upon the University of Rochester for five days next month
for the biggest conference of the decade on coherence and quantum
optics. The Seventh Rochester Conference on Coherence and Quantum
Optics, long considered the world's premier conference in the
field, will be June 7-10 on campus.

Scientists will discuss the nature of light and the many
surprising ways in which light interacts with matter. Among the
topics: cooling atoms almost to a standstill; exploring the
boundary between classical and quantum physics; results from new
types of lasers, including tiny one-atom micro-lasers; better
ways to generate, clean and control laser beams; and subtle ways
in which energy can be redistributed among different wavelengths
as light propagates.

The conference will include tutorials by top names in the
field, including Claude Cohen-Tannoudji of Paris, and German
physicists Herbert Walther and Wolfgang Schleich. More than 25
scientists will give invited lectures, and more than 250 will
present their work in poster sessions and in rapid 1.5-minute
presentations.

The conference, held at the University every five or six
years since 1960, will take place along with a conference on
Nonlinear Dynamics in Optical Systems and a Symposium on Spectral
Effects in Collective Phenomena.

At about the same time that the first conference took place,
the first laser was invented, and since then the conferences have
proven to be a record of advances that cover a wide range of
optical physics, including lasers, optical communications, and
many kinds of basic phenomena involving light and atoms. Even so,
many scientists who will attend the meeting are still asking
fundamental questions in areas such as quantum mechanics, whose
predictions even Einstein had trouble accepting.

The conference is sponsored by the American Physical
Society, the Optical Society of America, the University, and the
International Union of Pure and Applied Physics.
trSELECTED TOPICS AT THE SEVENTH ROCHESTER CONFERENCE
ON COHERENCE AND QUANTUM OPTICS

Lasing without population inversion -- a new type of laser

Scientists will discuss a newly discovered process, "lasing
without population inversion," that is unexpected, given the laws
of physics that govern lasers.

In a traditional laser, atoms are pumped full of light and
then release that light in sync. These new types of lasers appear
to work very differently from conventional lasers; the atoms do
not seem to store as much light as previously thought before
lasing. The process would have implications for the construction
of X-ray or ultraviolet lasers. Presenters include Marlan Scully
of Texas A&M and Olga Kocharovskaya of the former Soviet Union.

Laser cooling -- coldest spot in the universe

Several scientists will present their latest results on
laser cooling, where laser beams are used to bombard an atom to a
near standstill, cooling it to just a fraction of a degree within
absolute zero, nearly the coldest temperature possible in the
universe. At these temperatures, atoms begin exhibiting strange
interference effects, acting less like discrete particles and
more like waves. For instance, physicists have shown that a
single ultra-cold atom can travel down separate paths and
interfere with itself. Among the applications being investigated:
compact super-precise clocks, and "optical tweezers" that
scientists can use to isolate individual atoms and even living
cells.

Presenters in this area include Claude Cohen-Tannoudji of
Paris, Nicholas Bigelow of Rochester, and David Pritchard of MIT.

Classical vs. quantum mechanics

For much of the early half of this century, some of the
greatest physicists of all time -- such as Bohr, Einstein, and
Born -- argued over the true meaning of the laws of quantum
mechanics. Classical physics rules the world that most of us are
familiar with, but in the world of the atom, quantum mechanics is
necessary to explain the observations scientists routinely see in
the laboratory. The domain where classical physics breaks down,
and where somewhat larger objects demonstrate bizarre quantum
behavior, has long intrigued physicists.

Now, advances in short-pulse lasers have made possible the
creation of huge atoms, sometimes one micron in diameter, that
display the "classical" behavior of an electron orbiting a
nucleus for a short period of time -- systems as small as atoms
are behaving "classically." Meanwhile, engineers are creating
transistors and other structures smaller than a millionth of a
meter, a domain where quantum laws reign. Such experiments are
allowing them to test some of the tenets of quantum mechanics.

A "CT scan" of a molecule

Most people are familiar with computerized tomography (CT)
scans used by physicians to take a series of images of a
patient's body and then use computers to reconstruct a three-
dimensional image of the body.

Now, by taking advantage of recent results in quantum
optics, scientists are using very similar techniques to take new,
more complete 3D images of molecules and even photons. They do
this by reconstructing the interference pattern created by a
single photon or molecule. The techniques give scientists the
wave function of a system, a key to fully understanding the
behavior of a system.

Atom optics

One rapidly growing area is atom optics, where scientists
use atoms instead of photons to examine objects. Scientists are
looking at atom optics to design more sensitive ways to detect
gravity, or even to use atoms to help make computers chips.
Scientists think that atom microscopes, atom interferometers, and
even atom lasers are possible.

Shifting frequency of light

Many laboratories are demonstrating a mechanism discovered
not long ago at the University of Rochester to shift the spectrum
of light as it travels through space. Potential applications of
this effect, known as the "Wolf Effect," include more rapid
astronomical measurements and new ways to encode signals. Most of
the Symposium on Spectral Effects in Collective Phenomena is
devoted to this topic.

Transparency -- using one laser beam to "fix" another

Conference participants will discuss new ways to use one
laser beam to control another one. Using one beam to modulate or
even improve another could have applications in optical
computing, for instance, or in telecommunications or satellite
communications, where laser beams must travel long distances
through the atmosphere. Presenters of this work on transparency
include Joe Eberly at Rochester, Klaus Bergmann of Germany, and
Steve Harris at Stanford.

About the University of Rochester
The University of Rochester (www.rochester.edu) is one of the nation's leading private universities. Located in Rochester, N.Y., the University gives students exceptional opportunities for interdisciplinary study and close collaboration with faculty through its unique cluster-based curriculum. Its College, School of Arts and Sciences, and Hajim School of Engineering and Applied Sciences are complemented by its Eastman School of Music, Simon School of Business, Warner School of Education, Laboratory for Laser Energetics, School of Medicine and Dentistry, School of Nursing, Eastman Institute for Oral Health, and the Memorial Art Gallery.